Fix UI: move theme+CSS into gr.Blocks() so they apply regardless of launch method

Theme and CSS were previously only passed to launch() which was lost during
the HF Spaces refactor. Moving them into build_app() fixes local + HF runs.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/agents/app.py

@@ -948,7 +948,13 @@ def clear_session():
 # ─────────────────────────────────────────────────────────────────────────────
 
 def build_app():
-    with gr.Blocks(title="Odin — Drilling Intelligence") as app:
+    _theme = gr.themes.Soft(
+        primary_hue="emerald",
+        secondary_hue="slate",
+        neutral_hue="slate",
+        font=gr.themes.GoogleFont("Inter"),
+    )
+    with gr.Blocks(title="Odin — Drilling Intelligence", theme=_theme, css=CUSTOM_CSS) as app:
 
         answer_state = gr.State(None)  # holds export payload dict
 
@@ -1063,9 +1069,5 @@ demo, _figures_dir = _make_demo()
 
 
 if __name__ == "__main__":
-    demo.launch(
-        server_name="0.0.0.0",
-        server_port=7860,
-        share=False,
-        allowed_paths=[str(_figures_dir)],
-    )
+    demo.launch(server_name="0.0.0.0", server_port=7860, share=False,
+                allowed_paths=[str(_figures_dir)])